The present disclosure relates generally to an airfoil trailing edge, and more particularly, to a cooled turbine airfoil trailing edge.
Commonly, in a non-limiting example a cooled airfoil turbine includes a leading edge and a trailing edge. Hot fluids on an exterior airfoil surface of the turbine, combined with aggressive high fluid velocities at the trailing edge, lead to high heat fluxes when the material temperatures are limited to reasonable values. The heating of the trailing edge leads to deterioration and shorter life of the trailing edge. Different approaches have been employed in the past to reduce the heating of the trailing edge. A typical example of one such approach is to increase a thickness of the trailing edge, thereby allowing internal cooling of the trailing edge to reduce the deterioration of the trailing edge due to the applied heat flux. However, it is generally known that the thickness of the trailing edge is inversely proportional to the aerodynamic efficiency of the airfoil. Therefore, increasing the thickness of the trailing edge adversely affects the efficiency of the airfoil. In contrast, reducing the thickness of the trailing edge may result in rapid deterioration of the trailing edge if sufficiently effective cooling means are absent.
Some airfoils employ a cooling system to provide cooling to the trailing edge. One such approach is airfoil pressure side bleed slots where an aft portion of the airfoil pressure side is formed as a series of slots with intermediate lands during formation of the airfoil via a casting process. The bleed slots are connected to internal cooling channels and provide for a flow of a cooling fluid at the trailing edge. The cooling fluid reduces the temperature of the heated trailing edge. However, the cooling effectiveness typically decreases beyond the point of good durability as a result of inlet effects. More specifically, radial feeding of the cooling flow may induce flow distortion or separation in the trailing edge coolant flow that leads to low film effectiveness and resultant high metal temperature. This results in undesirable costs and inefficiency of the airfoil as well as a short part lifing. Therefore, obtaining sufficient cooling over the trailing edge remains a challenge.
In addition, the amount of cooling air used to cool the trailing edge is of issue. In many designs, the cooling flow rate in the trailing edge is greater than required to achieve effective cooling, but constrained by the manufacturing and the dimensions that can actually be achieved. Therefore, an improvement that allows for the use of less cooling flow, yet manufacturable, will lead to a more efficient engine.
It would therefore be desirable to provide a novel cooled airfoil to address the aforementioned issues.